The Short Messaging System (SMS) and the Multimedia Messaging System (MMS) have been used prolifically for personal messaging and are becoming increasingly popular as mediums for communicating advertising information. For example, information services can be configured to generate alerts via SMS or MMS, and these can be modified to include advertisement information; a system configured to provide such a service is described in international patent application having publication number WO01/22748. In addition to transmitting information via these individual and somewhat self-contained messages, information can be transmitted from information sources as Really Simple Syndication (RSS) feeds, audio streams, video streams, or text streams. International patent application having publication number WO01/31497 describes inserting advertisement objects into a video stream, and US patent having publication number U.S. Pat. No. 5,260,778 describes inserting messages such as emergency messages into a video channel. In systems according to both of these publications, the stream of data is modified so as to include a message, thereby notifying the content of the message to a viewer during viewing of or listening to the data stream.